The present invention relates to a method and apparatus for filling petri dishes.
As is well known, in order to detect the presence or absence of certain microorganisms, it is conventional to situate a specimen which may contain the suspected microorganism on a suitable nutrient, usually agar situated in a petri dish. Then the petri dish with the specimen on the agar therein is placed in a suitable incubator where under carefully maintained atmospheric conditions the culture is grown and thereafter examined to determine whether or not certain microorganisms are present.
Petri dishes of the above type are widely used in research and industry. Such petri dishes normally include a lower dish member containing a given quantity of agar and an upper lid member which normally covers the lower dish member. The upper lid member and lower dish member of the petri dishes can be inexpensively manufactured in large quantities inasmuch as they are simply clear plastic components which require only that the upper lid member fit loosely over the lower dish member. However, the costs of petri dishes of the above type are rendered undesirably high because of the procedures required in connection with filling the lower dish member with a given quantity of agar. These procedures require the upper lid member to be removed from the lower dish member, a given quantity of agar to be filled into the lower dish member, whereupon the petri dish is closed by situating the lid member over the filled lower dish member, and of course the agar sets to assume a solid condition upon cooling.
At the present time, the conventional methods and apparatus used in connection with filling petri dishes are relatively complex and time consuming. It is thus difficult to prepare filled petri dishes at a low cost. Furthermore, since the agar is in a liquid condition when it is filled into the lower dish member of the petri dish, care must be taken on one hand to avoid the spilling of the liquid agar and on the other hand to assure that the agar has a uniform depth in the lower dish member of a petri dish. If in an attempt to reduce costs the procedures in connection with filling the petri dishes are carried out too rapidly, spilling of the agar occurs and, particularly where a small amount of agar is situated in a petri dish, the agar does not have a uniform depth.